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02-27-2022, 02:03 AM   #1
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Use of wireless flash underground - request for advice

Hello all.

I am in need of advice about remote flashes for underground photography. In my case this is relatively narrow underground mining excavations (5m x 5m typical dimensions) rather than large caves.

My ideal setup is one or two standalone flashes that I can place in the excavation to illuminate the area, to be triggered by my K-70. I know the K-70 has various wireless functions and other Pentax equipment has some wireless communications capabilities. Do these extend to triggering flash units, or will I need an additional remote/wireless trigger?

Critical for me is I cannot mount a flash on the hotshoe, nor use the in-built flash, as this creates a huge amount of 'snow' when the camera focuses on dust suspended in the air. I think for this reason I will not be able to optically trigger the flash units.

I am open to good quality third-party equipment as well. I see a lot of recommendations for Godox flash units here.

Many thanks. Stuart.

02-27-2022, 04:24 AM   #2
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QuoteOriginally posted by Geo_Stuart Quote
I am in need of advice about remote flashes
I would usually recommend radio triggers over optical triggering as you are not limited by line-of-sight issues. I use Cactus V6II triggers on my K-1 (one transmitter on the hotshoe and one receiver on each remote flash), but unfortunately they are no longer in business.

I would have thought that for your use optical triggering would work just as well however. Now the K70 cannot use the built-in flash as a controller in P-TTL mode, so if you wanted to use P-TTL with optical triggering, you would need a flash on the hotshoe in addition to your remote flashes. You are able to choose between Master/Controller for the hotshoe flash, and in the latter mode it will not add to the actual exposure.

I would have thought that P-TTL mode would not be the best for your use as I imagine you would get brighter images than you wish. So manual flash control may be preferred.

Your options are:

1. get radio triggers
2. use optical triggering with a flash on the hotshoe in either Master/Controller mode
3. Use the built in flash to optically trigger the remote flashes in "dumb" flash mode. This means the remotes will fire when they see the built in flash fire. The remotes will fire at a pre-set output, and you will need to adjust them individually.

Radio triggers will give the best control options, not least being able to adjust each flashes output from your shooting position.

I would suggest you focus first (maybe using a torch), then set the camera to manual focus mode, so there is no AF going on for the actual capture.
02-27-2022, 06:55 AM   #3
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The flash on camera doesn't have to flash. It can trigger via the infrared.

You could light paint as the simplist solutuion. Block the light from seeing the camera and walk shining on what you want to paint in. Alternatively composite images in post.

The radio triggers have the most control. Some allow either ttl or individual control of each light from the camera. They can have trouble with interference. A concrete wall between can block them. That might matter in a mine.

You can use a chain. Trigger flash off camera from camera to trigger
More flashes in slave in view of the intermediate flash.
02-27-2022, 12:17 PM   #4
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Here's another radio control alternative:

https://www.adorama.com/fprrr2propn.html?

and several of these:

https://www.adorama.com/fplfsmminip.html?origterm=flashpoint+zoom...hredirect=true

These are compatible with each other and are stated to have considerable distance range between the transmitter which sits on your camera and the slave flashes which can be channelized if desired.

02-27-2022, 01:32 PM   #5
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You don't seem to have flashes yet, so I would recommend to start with a system that has radio-triggers built into the flashes as a compact and robust solution.

If you have enough time on the set to adjust flash power manually, an option would be the Yongnuo system: two YN560 flashes (III or IV, the later can also serve as a master) and the YN-560TX controller, plus two sets (2 x 2 x 4, or more if you need A LOT of shots) good NIMH accumulators, such as Eneloop Pro or equivalent. The controller goes onto the camera and allows you to control settings for both flashes individually, if needed. The YN560 IV can also be mounted on the camera and control extra flashes, but the UI isn't great.

The Godox system, which you mentioned, has a lot more features and range of flashes - simple NIMH-Powered ones (small and big), Li-Ion powered speedlights such as the V1 and battery-powered studio strobes, all supporting P-TLL and HSS for Pentax, on camera with the Pentax-specific models and remote also for the universal models. Adorama sells them rebranded as Flashpoint, including specific controllers just available there, compatible with Godox's protocol. Highly recommended if you plan a lot of flash work in the future.

Both radio trigger systems have worked for me flawlessly over the indicated distances.
02-27-2022, 02:39 PM - 1 Like   #6
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Godox has a low-cost radio-controlled flash system which would probably work well for you. Radio doesn't emit any light, so using a transmitter on top of your hotshoe to remotely control the flashes won't cause the dust-orb issue you mention.

I would not recommend getting Yongnuo YN-560 gear, since that system is hard to expand and doesn't offer any radio-controlled P-TTL options. Godox has their own $65 single-pin manual speedlight (TT600) you can use in their system if you need a low-cost reliable solution for multiple lights/possibly disposable/trashable units. The main thing to know here is that most of these 3rd-party Chinese speedlights are not weather-sealed, so if you're caving in wet conditions, you may also want to consider how to protect the flashes. I once saw a great DIY PVC design to protect these types of flashes for wakeboard photography on the Strobist. You could probably DIY something similar up. Because the flashes can be radio controlled remotely, you won't need access to the physical UI of the flash once it's turned on and put into a protective case. You might also need to think about protecting your transmitter a bit, though.

On the Godox side of the fence, you have the following off-camera speedlight options:
  • TT350-P ($85). Mini TTL/HSS speedlight. Can be used in TTL/HSS on-camera as well as off. But less powerful than a full-sized speedlight (2xAA, not 4xAA), and a smaller radio range as a transmitter; only 16 channels vs. 32 on the other speedlights.
  • TT600 ($65). Full-sized single-pin manual speedlight. Cannot do TTL, only does HSS over radio, not on camera. Cannot be firmware upgraded.
  • TT685-C ($110). For-Canon version. Can be firmware updated to do P-TTL /HSS over radio, but is only TTL/HSS on a Canon hotshoe.
  • V860 II ($180). Same as the TT685-C, only all flavors can be firmware updated for P-TTL radio use. Also has a li-ion battery pack for 2.8x the battery life of 4xAA in the TT685.
  • V1-P ($260). Top of the line round-headed speedlight for Pentax.

There are also the $300 and up AD Witstro models that are basically off-camera li-ion powered TTL/HSS bare bulb strobes. Some have a lot more power than a speedlight. But at the cost, these might be prohibitive for usage where you could damage a unit.

---------- Post added 02-27-22 at 01:54 PM ----------

QuoteOriginally posted by JensE Quote
If you have enough time on the set to adjust flash power manually, an option would be the Yongnuo system: two YN560 flashes (III or IV, the later can also serve as a master) and the YN-560TX controller, ...
Just me, but the Godox system with, say, an XPro-P ($70) and the TT600 speedlight ($65) is similarly priced and speced to a YN-560-TX ($45) + YN-560 IV ($85), and has some interesting functional tradeoffs. While the Yongnuo YN-560 may get you one more group (6 instead of 5) and does remote wakeup and zoom control with the single-pin manual flashes, which Godox doesn't (it can only zoom TTL speedlights). On the flip side, Godox gives you HSS with the TT600 and an XPro-P, and also offers you the ability to add any of Godox's other lights, TTL or Manual-only, speedlight or li-ion bare bulb flash, or AC-powered plug-in studio monolight into the system. And there's P-TTL support in the Godox radio system. And it's mostly cross-brand support with Canon, Nikon, Sony, Fuji, and Olympus/Panasonic.

Yongnuo is great and seven or eight years ago was the main recommendation for Strobists on the cheap, but Godox has since left them in the dust in terms of features, compatibility, and expansion, primarily by having a single unified radio system. Yongnuo still makes solid gear, but unless you're a Canon RT shooter, or you need P-TTL with a YN-565EX for on-camera use, there's not really an advantage in going with them. And there are more pitfalls with them.

At this time, Yongnuo, iirc, has something like five separate incompatible radio triggering systems. The 560/60x manual system, the 622 TTL system (which only works for Canon or Nikon and doesn't work cross-brand), the Canon-only RT system, their new YN-560 Pro system (which is trying to tie together the 622 and 560 systems and not quite succeeding), and their yet-again separate and incompatible TTL Sony system. It's a complete mess trying to figure out what works with what in which manner, and it's a rabbit hole I try to steer people away from these days.

'cause Godox TT600. Even the Strobist likes it.
02-27-2022, 03:09 PM   #7
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QuoteOriginally posted by inkista Quote
Yongnuo is great and seven or eight years ago was the main recommendation for Strobists on the cheap, but Godox has since left them in the dust in terms of features, compatibility, and expansion, primarily by having a single unified radio system.
I agree, and that's why I 'highly recommended' them. I just mentioned the YN 560's, because they are fairly reliable, can often be had for next to nothing on the used market and they are maybe a bit simpler to use. The only thing that they do a lot better than my Godoxes is the optical slave mode (S1/S2).

02-28-2022, 08:49 AM   #8
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QuoteOriginally posted by Geo_Stuart Quote
Critical for me is I cannot mount a flash on the hotshoe, nor use the in-built flash, as this creates a huge amount of 'snow' when the camera focuses on dust suspended in the air.
SCUBA divers (and cave divers) have the same problem with less-than-clear water, unwanted hovering particles, that are close to the camera, in the environment. The solution is to illuminate from each side, sideways towards each other, not on-axis (camera-lens axis that is), to avoid direct reflection to the camera.

I recommend the Godox XPro-P trigger plus two or more pairs of Godox TT350, each within a translucent plastic bag. Or inside Tupperware boxes or inside any kind of protective box or shell. Can be just an open-ended piece of PVC pipe that has 2 1/2 inch (~7cm) diameter and 6 inch length and some translucent plastic as a lid, held in place by a rubber band.

The flashes do not need extra radio receivers, their electronics has that inbuilt. Power is not a concern if you carry enough AA batteries. For the size of the illuminated area the small flashes may be enough and they can be kept at their widest zoom setting. More power from the bigger size Godox TT600 flashes can also be useful, if they are used at less than full power, say, 1/4. But TT600 use 4 AAs, each.

---------- Post added 02-28-22 at 06:09 PM ----------

Bigger, brighter, more powerful flashes, with a higher Guide Number (GN) can also mean that the useful end gets hot. Any protective enclosure has to consider that. More powerful flashes that you don't fire at full nominal power output, meaning a setting of 1/4 or 1/8th power, do not get so hot so fast. For a static scene you may consider a long exposure of several seconds (camera in bulb mode, on tripod) and multiple bursts of small-power flash that are triggered by hand, where the trigger is held in the hand, it is not even mounted on camera. You may even walk around, briefly illuminating certain parts of the walls, similar to what is called "light-painting" in night photography.
02-28-2022, 02:11 PM - 1 Like   #9
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QuoteOriginally posted by CristiC Quote
I recommend the Godox XPro-P trigger plus two or more pairs of Godox TT350
I get why you're recommending the TT350-P as the unit to purchase and it's a terrific choice, particularly if you want a number of smaller units. But if a flash is only going to be used off-camera, then the TT600 (which ditches TTL control) is only $65, and a TT685C ($110) can be firmware-updated for TTL/HSS control over radio from an XPro-P. Both are also full-sized speedlights using 4xAAs, and can output 2x (1EV) more light than a TT350 can. The TT350-P is not the only low-cost speedlight option for off-camera PTTL, and just my personal experience, the TT685 and TT600 are more ruggedly built than a TT350.
03-07-2022, 05:42 AM   #10
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You might be able to to trigger optically (without the "snow") by bouncing the flash off the ceiling. If needed, you can make an effective snoot using black craft foam and a rubber band. I'd prefer the radio controller solution, but this might help reduce your costs if you already own the flashes needed.
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